The 1800 year old hypocaust and its covering mosaic floor were uncovered during excavations in Verulamium Park in the 1930s by Sir Mortimer & Tessa Wheeler.

It was decided to leave these in their original Roman location where they formed part of the reception and meeting rooms of a large town house. The preserved section was part of a suite that originally extended almost twice the surviving length of the room.

What is a hypocaust?

Roman hypocaust systems allowed hot air to circulate beneath the floor and through the walls of buildings. Floors were raised on brick columns (pilae) or, as in this case, trenches were cut below the floor to allow the hot air through. Part of the mosaic has collapsed into the trench below.

The mosaic covering the hypocaust was made of tesserae (small cubes) of cut stone or tile. These were set into a thin layer of fine mortar which was spread over a concrete floor. The tesserae were grouted with mortar and polished with abrasive stones. The floor may have been polished with beeswax to enhance the colours.